To survey and record the understorey bird species diversity along elevational gradients on the northeastern slope of Mt. Makiling, Luzon, Philippines, six sampling sites with 20 netting stations were established between low forest edge up to mossy forest in the following elevational ranges (m asl): 40-199 (forest edge), 200-399 (secondary lowland forest with built-up areas), 400-599 (secondary lowland forest), 600-750 (mixed grassland and forest), 751-899 (midmontane forest) and 900-1094 (mossy forest). Mist-netting was done from July 2008-May 2009. A total of 169 individuals belonging to 29 bird species in 19 families were observed from the different elevations. Understorey bird species richness and diversity were highest at midmontane forest and lowest at mossy forest. There was no particular pattern along the various elevational gradients for the computed species diversity indices (H’). Majority of the birds were both common and endemic species. Decline of understorey bird diversity in Mt. Makiling is attributed to the massive alteration of forest communities and their large scale conversion to agricultural area and human settlement.

Key words: understorey bird diversity, bird richness, habitat diversity, mist-netting, elevation gradient, Mt. Makiling, Luzon, Philippines